We found the air of the table-land fresh and invigorating after the excessive heat of the valleys below. For three days we travelled northwards across the plateau. Our first stage was Haibel Gabrein. This is, as it were, the culminating point of the whole district; it is 4,150 feet above the sea. From it the table-land slopes gently down to the northward towards the main valley of the Hadhramout, and eastwards towards the Wadi Adim. After two days more travelling we approached the heads of the many valleys which run into the Hadhramout; the Wadis Doan, Rakhi, Al Aisa, Al Ain, Bin Ali, and Adim all start from this elevated plateau and run nearly parallel. The curious feature of most of these valleys is the rapid descent into them; they look as if they had been taken out of the high plateau like slices out of a cake. They do not appear to have been formed by a fall of water from this plateau; in fact, it is impossible that a sufficient force of water could ever have existed on this flat surface to form this elaborate valley system. In the valleys themselves there is very little slope, for we found that, with the exception of the Wadi Adim, all the valley heads we visited were nearly of uniform height with the main valley, and had a wall of rock approaching 1,000 feet in height, eaten away as it were out of the plateau. We were, therefore, led to suppose that these valleys had originally been formed by the action of the sea, and that the Hadhramout had once been a large bay or arm of the sea, which, as the waters of the ocean receded, leaving successive marks of many strands on the limestone and sandstone rocks which enclosed them, formed an outlet for the scanty water-supply of the Southern Arabian highlands. These valleys have, in the course of ages, been silted up by sand to a considerable height, below which water is always found, and the only means of obtaining water in the Hadhramout for drinking purposes, as well as for cultivation, is by sinking wells. The water of the main valley is strongly impregnated with salt, but is much sweeter at the sides of the valley than in the centre. No doubt this is caused by the weight of the alkaline deposits washed down from the salt hills at Shabwa, at the head of the main valley. The steep, reddish sandstone cliffs which form the walls of these valleys are themselves almost always divided into three distinct stories or stratifications, which can be distinctly seen on the photographs. The upper one is very abrupt, the second slightly projecting and more broken, and the third formed by deposit from above. The descent into the valley is extremely difficult at all points. Paths down which camels can just make their way have been constructed by the Bedouin, by making use of the stratified formation and the gentler slopes; but only in the case of the Wadi Adim, of all the valleys we visited, is there anything approaching a gradual descent.